► LNG (Liquefied Natural Gas) is one of the fastest growing energy sources in the U.S. to fulfill the increasing energy demands. In order to meet…
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▼ LNG (Liquefied Natural Gas) is one of the fastest growing energy sources in the
U.S. to fulfill the increasing energy demands. In order to meet the LNG demand, many
LNG facilities including LNG importation terminals are operating currently. Therefore,
it is important to estimate the potential risks in LNG terminals to ensure their safety.
One of the best ways to estimate the risk is LOPA (Layer of Protection Analysis)
because it can provide quantified risk results with less time and efforts than other
methods. For LOPA application, failure data are essential to compute risk frequencies.
However, the failure data from the LNG industry are very sparse. Bayesian estimation is
identified as one method to compensate for its weaknesses. It can update the generic data
with plant specific data.
Based on Bayesian estimation, the frequencies of initiating events were obtained
using a conjugate gamma prior distribution such as OREDA (Offshore Reliability Data)
database and Poisson likelihood distribution. If there is no prior information, Jeffreys
noninformative prior may be used. The LNG plant failure database was used as plant
specific likelihood information. The PFDs (Probability of Failure on Demand) of IPLs (Independent Protection
Layers) were estimated with the conjugate beta prior such as EIReDA (European
Industry Reliability Data Bank) database and binomial likelihood distribution. In some
cases EIReDA did not provide failure data, so the newly developed Frequency-PFD
conversion method was used instead. By the combination of Bayesian estimation and
LOPA procedures, the Bayesian-LOPA methodology was developed and was applied to
an LNG importation terminal. The found risk values were compared to the tolerable risk
criteria to make risk decisions. Finally, the risk values of seven incident scenarios were
compared to each other to make a risk ranking.
In conclusion, the newly developed Bayesian-LOPA methodology really does
work well in an LNG importation terminal and it can be applied in other industries
including refineries and petrochemicals. Moreover, it can be used with other frequency
analysis methods such as Fault Tree Analysis (FTA).
Advisors/Committee Members: Mannan, M. Sam (advisor), Hall, Kenneth R. (committee member), Malav?C?r O. (committee member).

► Ammonia refrigeration systems are widely used in industry. Demand of these systems is expected to increase due to the advantages of ammonia as refrigerant and…
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▼ Ammonia refrigeration systems are widely used in industry. Demand of these
systems is expected to increase due to the advantages of ammonia as refrigerant and
because ammonia is considered a green refrigerant. Therefore, it is important to evaluate
the risks in existing and future ammonia refrigeration systems to ensure their safety.
LOPA (Layer of Protection Analysis) is one of the best ways to estimate the risk.
It provides quantified risk results with less effort and time than other methods. LOPA
analyses one cause-consequence scenario per time. It requires failure data and PFD
(Probability of Failure on Demand) of the independent protection layers available to
prevent the scenario. Complete application of LOPA requires the estimation of the
severity of the consequences and the mitigated frequency of the initiating event for risk
calculations.
Especially in existing ammonia refrigeration systems, information to develop
LOPA is sometimes scarce and uncertain. In these cases, the analysis relies on expert
opinion to determine the values of the variables required for risk estimation. Fuzzy
Logic has demonstrated to be useful in this situation allowing the construction of expert
systems.
Based on fuzzy logic, the LOPA method was adapted to represent the knowledge
available in standards and good industry practices for ammonia refrigeration. Fuzzy
inference systems were developed for severity and risk calculation. Severity fuzzy inference system uses the number of life threatening injuries or deaths, number of
injuries and type of medical attention required to calculate the severity risk index.
Frequency of the mitigated scenario is calculated using generic data for the initiating
event frequency and PFD of the independent protection layers. Finally, the risk fuzzy
inference system uses the frequency and severity values obtained to determine the risk of
the scenario.
The methodology was applied to four scenarios. Risk indexes were calculated
and compared with the traditional approach and risk decisions were made.
In conclusion, the fuzzy logic LOPA method provides good approximations of
the risk for ammonia refrigeration systems. The technique can be useful for risk
assessment of existing ammonia refrigeration systems.
Advisors/Committee Members: Mannan, Sam M. (advisor), Hall, Kenneth R. (committee member), Malave, Cesar O. (committee member).

► The concept of risk pervades everyday life. In modern times, study of industry- or technology-risk is necessary and essential because not only it is closely…
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▼ The concept of risk pervades everyday life. In modern
times, study of industry- or technology-risk is necessary and
essential because not only it is closely linked with people’s
lives, but also those risks can lead to serious consequences.
Chemical and allied industries (petroleum, gas, etc.), with their
both high-risk and high-profit nature, take on important roles in
technology-risk studies. Many techniques have been developed to
address risk issues, such as Fault Tree Analysis, Hazard and
Operability Analysis and Layer of Protection Analysis (LOPA). Most
of them identify or quantify risks from an equipment-reliability
perspective, and human factors are seldom taken into account. In
this thesis, a risk evaluation method, TopN method, focusing on
human perception is developed. It can be seen as a complementary
layer to LOPA, where human supervision, alarm and control should be
the core considerations. The main purpose of this approach is to
detect gaps between work managers’ and operators’ risk perceptions.
A pilot study was done with the proposed method and followed by
some analyses and visualizations of the results. Similarities and
differences in human risk perceptions are easy to check with the
help of this method and its visualization tools. In conclusion,
TopN method is straightforward and time-saving, and it is adequate
to be a complementary technique to LOPA taking human risk
perception into consideration.

This work deals with a novel microscopy technique based on the ultra-low one-photon absorption (LOPA) mechanism of photosensitive materials for fabrication of arbitrary two- and three-dimensional (2D, 3D) submicrometer structures. First, we theoretically investigated the intensity distribution at focusing region of a high numerical aperture objective lens as a function of various working conditions, such as propagation of light mismatched refractive index and/or absorbing media. We demonstrated that when working with refractive index mismatch-free and very low absorption conditions, the light could be focused deeply inside the material, allowing a 3D optical manipulation. We then demonstrated experimentally the use of this simple technique for fabrication of desired structures. Different 2D and 3D structures, with a feature as small as 150 nm, have been created in SU-8 photoresist by using a low power and continuous-wave laser emitting at 532 nm. Furthermore, we demonstrated that it is possible to fabricate a polymer-based photonic structure containing a single nanoparticle (NP), by using a double-step method. Indeed, the LOPA microscopy…

► "Risk assessment and identification in the early stages of any project is critical to the success of that project from time, budget and cost…
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▼ "Risk assessment and identification in the early stages of any project is critical to the success of that project from time, budget and cost prespective [sic]. Identifying unacceptable risks and making provisions to mitigate those, can reduce the uncertainty in the project and ensure its smooth completion and closure. Various techniques have been developed over time to identify and quantify risks. Inspite of all the available research on risk management tools, accidents continue to happen and projects consistently fail.
The objective of this study is to first, determine the generic risks that can be encountered by a project. A list of generic risks will be prepared and validated by surveying managers from various industries. These risks will be prioritized to provide managers with a generic risk matrix which can be readily applied to cross-industry projects. The second part of the study involves the use of Layers of Protection Analysis (LOPA), to analyze two past catastrophic accidents. The financial industry and the Space Shuttle program will be considered to produce the required analysis. LOPA models will be created to expose shortcomings in the failed projects and provide lessons to be learned in order to avoid future disasters. This research will provide a unique direction and a new tool for project managers to deploy this technique of building protection layers to prevent, protect and/or mitigate risks encountered by their system/project" – Abstract, page iv.